FAQ: The Deadly Ebola Virus

Editor's note: This story was updated on May 11, 2015, with the WHO declaring Liberia’s Ebola epidemic at an end; new case numbers; and a report on the Ebola virus discovered in a survivor’s eye.

April 4, 2014 -- Perhaps no virus strikes as much fear in people as Ebola, the cause of a deadly outbreak in West Africa.

The World Health Organization (WHO) reports more than 26,700 confirmed or suspected cases of Ebola as of May 9, 2015. More than 11,000 people have died in the largest Ebola outbreak ever recorded.

The majority of cases were in the three West African nations of Guinea, Liberia, and Sierra Leone. But on May 9, the WHO declared Liberia’s Ebola outbreak over. The agency said 42 days had passed since the last victim of the virus had been buried. The nation’s last Ebola patient was released from a treatment unit in March.

An infected U.S. health care worker arrived March 13 at the National Institutes of Health Clinical Center in Bethesda, MD, for treatment, the NIH said in a statement. The person, who was not identified, caught the virus while working as a volunteer at an Ebola treatment center in Sierra Leone, the NIH said.

The health care worker, who at one point was in critical condition, was released from the clinical center on April 9, and is “no longer contagious to the community,” the NIH said in a statement.

No further information was released about the health care worker, who was the second American to be treated at the NIH facility. The first was Nina Pham, 26, a Dallas nurse who caught Ebola after treating Thomas Eric Duncan, a Liberian man who later died. Pham recovered from the virus.

She was one of two nurses at Texas Health Presbyterian Hospital who caught Ebola after treating Duncan. The second, Amber Vinson, 29, also recovered after being treated at Atlanta’s Emory University Hospital.